1) Field of the Invention
The present invention relates to a plastic housing and frame of back-lit illuminated signs which are produced by vacuum forming or thermo-press forming technology by using thermoformable polymeric plastic sheet material, and transparent or translucent plastic panels.
2) Description of the Prior Arts
The U.S. Pat. No. 5,509,223 Lighting System discloses that a highly reflective linear semi-circular reflector combined with tubular light source to create a consecutive and overlapped virtual images of the light source which provides a strong band of back lighting for an illuminated signs, and it's basic principles are applied to this invention as a part.
The Basics of edge illuminating mechanisms are also applied to the present invention to create a improved visual effect for an improved illuminated sign providing more variations in applications.
The housing of small size illuminated signs are normally made of various thermoformable polymeric plastic sheet such as ABS, styrene, poly-propylene, and it's color is normally very dark such as black or dark gray etc. to minimize it's visibility for the observers of the illuminated sign which is a basic requirement of the outer surface of the housing to enhance the illuminated graphics. But, a requirement of inner surface of the box is totally opposite to the requirement of the outer surface which should be the brightest possible to reflect the light energy emitted from light sources in maximum to make the illuminated sign face the brightest possible. To make a better inner surface of the housing, white paint have been coated on the inner surface of the housing to improve the reflectivity when a black or dark color sheet material is used.
To eliminate the cumbersome paint coating procedure, two sided thermoformable polymeric plastic sheet having a white and black on each faces is produced by using co-extrusion technology which can easily produce the housing with dark outer surface with white inner surface at one step of thermoforming.
In further, there are many different kind of combination of laminated termoformable sheet with highly reflective surface have been introduced, and it is commercially available in the market. But these sheet stocks are not enough to be competitive in the price and there is many technical difficulties in the process of a good thermoforming.
To produce an illuminated sign, a device to hold a sign face is essential, and sometimes a replacing mechanism of the sign face is also a requirement of which function is normally provided on frames which is holding the flange of housing and the sign face at one time, and there are many different designs to maximize the function of holding and replacing mechanism of the sign face in good shape of looking.